Monitor systems

ABSTRACT

A monitor system for detecting bent, broken, missing or otherwise mutilated operating elements in a cyclically operable machine (e.g., the knitting needles in a rotary knitting machine) comprising a sensing device for sensing passage of individual operating elements, a detector for detecting mutilated elements from the output of the sensing device to develop an error signal, and a range gate for blanking the detector for most of a complete cycle or period after each error signal. A counter develops a control signal to shut down the machine on a given count of error signals occurring in consecutive cycles; a strobe light actuated by the error signals locates the mutilated operating elements.

Unite States Patent Anthony 5] Feb. 29, 1972 [54] MONITOR SYSTEMS [2]] Appl, No.: 14,053

3,158,850 11/1964 Potnanski ..340/261 x 3,343,158 9/1967 Tellerman.... 3,445,838 5/1969 Appleton ..340/324 Primary Examiner-David L. Trafton Attorney-Jennings, Carter & Thompson [5 7] ABSTRACT 521 11.5. ..340/259, 66/l57, 340/419 A sysem detecfing bwke", missiflg or 511 1111.0. ..G08b 21/00 wise P P' Flemems F cyclically Operable [58] Field of Search ..340/259, 263, 267, 419, 324 R; P? needles a 66/157, 165; 235/92 FF, 92 PD, 92 TF; 307/1 16, machine) compn smg a sensmg device for sensing passage of 117 120 1nd1v1dual operating elements, a detector for detecting mutilated elements from the output of the sensing device to [56] References Cited develop an error signal, and a range gate for blanking the detector for most of a complete cycle or period after each error UNITED STATES T NTS signal. A counter develops a control signal to shut down the machine on a given count of error signals occurring in con- 3,529,445 9/1970 Bruse ..66/165 x Sew-we cycles; a Strobe light actuated by the Signals sathgrlell ett .235/6962/ locates the mutilated operating elements. an ene 23.... 3,261,009 7/1966 Stetten et al ..340/261 2 Claims, 6 Drawing Figures 4 u/se D/fferen Frequency Z3 Z7410! Anoma/y De factor Mach/)9 (antr PATENTEDFEBZQ I972 SHEET 2 UF 4 Afro/hays MONITOR SYSTEMS BACKGROUND OF THE INVENTION Knitting machines, as employed for production purposes in the textile industry, frequently comprise a large circular array of knitting needles mounted upon a needle cylinder that rotates at a relatively high speed. For example, a large knitting machine may utilize 500 to 1,000 needles and the speed of rotation may be of the order of 90 revolutions per minute, with the needles passing a given point on the rim of the needle cylinder at about one needle per millisecond. In these machines it is virtually impossible to detect runs, missing threads, and other imperfections by visual observation, because an operator cannot see the entire surface of the knitted cloth at any given time. Moreover, it is customary to have an operator control several machines so that he cannot maintain continuous observation of the output of any given machine. In many knitting machines, particularly those employed to knit fabrics having a looped surface that is sub sequently broken to afford a fleece surface, it is literally impossible for the machine operator to observe the quality of the base fabric because it is obscured by the looped surface.

When a run or other imperfection occurs in the output of a knitting machine, it frequently cannot be discovered until after substantial processing of the knitted fabric as by loopbreaking to produce a fleece surface, cleaning and dyeing. Often, entire large rolls of knitted material must be classified as reject because of runs or similar imperfections that have not been observed and in fact cannot be observed at the knitting machine.

Customarily, runs and other imperfections in machineknitted material are frequently attributed to poor quality yarn, and various machine adjustments. In connection with the present invention, however, it has been discovered that a large percentage of these defects in the knitted material result from broken, bent, missing, loose, or otherwise mutilated needles.

In this application, and in the appended claims, the term mutilated" is intended to refer to a needle or other similar operating element of a knitting machine or like apparatus that is bent or otherwise displaced from its normal position in the machine, that is completely missing, that is broken in one respect or another, or that is loose in its mounting in the array of individual operating elements in the machine.

In the past, it has been customary to rely upon inspection by skilled machine operators to determine whether the knitting machine needles are accurately aligned on the machine cylinder, with all needles in place and positioned to perform an effective knitting operation. Some limited mechanical aids and alignment devices have been available, but these have not assured complete and accurate alignment of the needles, even when a machine is shut down and the needles replaced. Thus, even with skilled operators, a machine may be thoroughly inspected and placed in operation, following a shutdown, and may immediately produce defective cloth. Effective inspection of the alignment of the needles in the machine has not generally been possible, using prior art techniques.

SUMMARY OF INVENTION It is a principal object of the invention, therefore, to provide a new and improved monitor system for a knitting machine or like apparatus of the kind comprising an array of individual operating elements, such as knitting needles, moving along a given path at a predetermined speed, to assure the presence, accurate alignment, and effective operation of those operating elements.

Another object of the invention is to provide a new and improved system for monitoring the individual operating elements of a knitting machine, or like apparatus of the kind comprising an array of individual operating elements moving at a relatively high rate of speed along a given path in a repetitive operating cycle, that affords effective continuing operation in an environment in which the monitoring system is subject to substantial electrical or mechanical noise, considerable dirt and other foreign material.

Another object of the invention is to provide a new and improved monitoring system for a knitting machine or like cyclically operable apparatus incorporating an array of individual operating elements moving at a predetermined speed along a given path that can detect the presence of any mutilated operating unit and also identify accurately the location of the mutilated element.

Another object of the invention is to provide a new and improved monitoring system of the kind described above that may be employed to detect operating elements that are approaching a failing condition, prior to the time of actual failure, and that can be employed to assure accurate setup of the machine as well as to detect mutilated operating elements. In this regard, a specific object of the invention is to provide a monitoring system having a readily and conveniently adjustable sensitivity to afford an accurate and effective means for machine setup.

Accordingly, the invention relates to a monitor system for an apparatus of the kind comprising an array of individual operating elements moving at a predetermined speed along a given path in accordance with a predetermined repetitive operating cycle. The monitor system comprises sensing means, located at one observation point on the path, for generating a sensing signal comprising a series of pulses each indicative of the passage of one operating element past the observation point. The system further comprises a pulse frequency anomaly detector, coupled to the sensing means, for generating an error in response to a material displacement in timing or marked reduction in amplitude of one of the sensing signal pulses, indicating passage of a mutilated operating element past the observation point. A range gate coupled to the detector, precludes the generation of consecutive error signals within a time interval corresponding to a major fractional portion, usually about 350, of the operating cycle of the apparatus. A counter is coupled to the detector for developing a control signal in response to a predetermined number of error signals occurring in consecutive operating cycles of the apparatus. Index means are mounted on the array of operating elements and a stroboscopic light source, located at a second observation point along the operating element path, illuminates the index in response to each error signal to enable a machine operator to identify the location of the mutilated operating element.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a monitor system constructed in accordance with one embodiment of the present invention;

FIG. 2 is a fragmentary elevational view illustrating the mounting of the sensing means and strobe light of the monitor system in relation to a knitting machine;

FIG. 3 is a schematic diagram of one suitable circuit for the monitor system of FIGS. 1 and 2;

FIG. 4 is a series of electrical waveforms illustrating circuit conditions in a part of the circuit of FIG. 3;

FIG. 5 is a series of waveforms illustrating circuit conditions for another part of the circuit of FIG. 3; and

FIG. 6 is a series of waveforms similar to FIG. 4 but illustrating a different operating condition.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 illustrates a monitor system 10, constructed in accordance with the present invention, applied to a rotary knitting machine. A part of the machine and some of the monitor system components are illustrated in FIG. 2. The knitting machine, FIG. 2, comprises a fixed base 11 and a rotary needle cylinder 12 rotating in the direction generally indicated by the arrow A. Needle cylinder 12 carries an array of equally spaced spring-steel knitting needles 13 mounted at equally spaced intervals around the needle cylinder. In a typical machine, each needle 13 is cast in a lead mounting block 14 and the block is mounted in the needle cylinder (FIG. 1).

In the particular knitting machine construction shown in FIGS. 1 and 2, each needle 13 has a resilient, flexible beard 15. It should be understood, however, that the monitor system of the present invention can be applied to knitting machines using needles of different constructions, including those with pivotally mounted components instead of the spring beards 15 Furthermore, the monitor system is applicable to other apparatus utilizing an array of individual operating elements generally comparable to the knitting needles 13, in which the operating elements move at a predetermined speed along a given path in accordance with a predetermined repetitive operating cycle.

Monitor system comprises a sensing device 16 mounted at a given observation point onthe path of the moving array of needles or other operating elements. The particular sensing device illustrated in FIG. '1 includes a permanent magnet 17 having two pole pieces 18 facing the needles 13 and having a configuration such that the beard 15 of each needle 13 comes in close proximity to the pole pieces 18 as the needles pass the observation point at which sensing device 16 is mounted. A typical mounting for sensing device 16, relative to the needle cylinder 12, is shown in FIG. 2. However, any mounting for the sensing device that will enable the sensing device to detect the passage of each needle can be employed.

Sensing device 16 (FIG. 1) further comprises a coil 19 mounted upon magnet 17 (the coil could also be wound upon a part of the pole piece structure). One terminal of coil 19 is connected to a limiter amplifier 20. The other terminal of the coil is returned to system ground. The output of amplifier 20 is connected to a differentiator circuit 21 which is in turn connected to a pulse-shaping amplifier 22. The output of amplifier 22 is connected to a pulse frequency anomaly detector 23. Detector 23 generates an error signal in response to any material displacement in timing or marked reduction in amplitude in the pulse signals supplied to the detector from amplifier 22, as described more fully hereinafter. Preferably detector 23 is provided with a means for adjusting its sensitivity, as generally represented in FIG. 1 by a variable resistor 82.

A range gate 24 is coupled to the output of detector 23. Like detector 23, range gate 24 is preferably provided with a sensitivity adjustment represented by a variable resistor 91. The output of the range gate, in turn, is coupled back to detector 23 in a feedback circuit for controlling operation of the detector to preclude the generation of consecutive error signals within a time interval corresponding to a major fractional portion of the operating cycle of the knitting machine. The feedback connection could be made ahead of the detector; for example, range gate 24 could be coupled back to any one of circuits 20-22. But the range gate control is preferably effected at the detector.

The output of detector 23 is also coupled to a counter 25 for developing a control signal in response to a predetermined number of error signals, provided those error signals occur in consecutive operating cycles of the knitting machine. Counter 25 is connected to a machine control circuit 26, which may constitute a switching circuit for shutting down the knitting machine. An alarm device 26A may also be actuated by the control signal from counter 25.

The output of error detector 23 is also connected to a stroboscopic light source 28. The strobe light 28 is located at a second observation point along the rim of needle cylinder 12, preferably closely adjacent the first observation point at which probe 16 is positioned (see FIG. 2). Strobe light 28 is focused on an index 29 on needle cylinder 12. Index 29 need not be precisely aligned with the individual needle positions in the array of needles 13 on the needle cylinder. However, the index should afford a sufficient number of identification points to enable a machine operator to locate a defective needle quickly and conveniently. A fixed marker 30 may be mounted on the knitting machine base in alignment with a strobe light 28 to assist in locating mutilated needles.

With the knitting machine in operation, each needle 13, as it passes sensing device 16, materially reduces the reluctance between the two pole pieces 18 of the sensing device. Each time this occurs, a surge of flux through the magnetic structure of sensing device 16 generates an electrical signal pulse in coil 19. Thus, the output of the sensing means comprising device 16 is a sensing signal constituting a series of signal pulses of given polarity, each pulse being indicative of the passage of one needle past the observation point at which device 16 is mounted. Timing of the individual pulses is determined by the spacing between the needles. If a given needle has a flattened beard 15, then the pulse will be markedly reduced in amplitude. This is equally true if the beard is broken off. In the case of a completely missing needle, no signal pulse is developed for that particular needle position. If the needle or the beard is bent to one side, the signal pulse developed by coil 19 occurs early or late in relation to the normal timing of the pulse for an unmutilated needle. Thus, the timing and amplitude of the signal pulses developed by the sensing device 16 affords full information with respect to virtually any form of mutilation that may occur with respect to needles 13.

The train of sensing signal pulses developed by sensing device 16 is amplified and limited in amplifier 20 and is differentiated in circuit 21, following which further shaping of the signal pulses occurs in amplifier 22. This particular sequence of circuits is not critical to the invention; however, it is usually necessary to afford some pulse-shaping circuits to provide a relatively clean pulse signal to error detector 23. The reference to a clean" signal should be understood to encompass some anomalies in addition to the desired pulses, since a knitting machine or other comparable industrial apparatus usually produces a variety of noise signals, due to both electrical and mechanical sources, caused by irregularities in operation of the machine itself. That is, the output signal from amplifier 22 excludes a substantial amount of recurring noise, such as 60 cycle power supply noise and noise resulting from cyclic rotation of the knitting machine, but some extraneous pulses may still be present in the signals supplied to detector 23.

Detector 23 generates an output signal, referred to herein as an error signal, only when one of the incoming pulse signals is markedly delayed with respect to its normal timing or is of such reduced amplitude as to indicate the presence of a mutilated needle. But the generation of a single-error signal is not utilized to directly actuate machine control 26 or alarm 26A because, as noted above, the incoming signal to detector 23 may include irregular pulses that do not truly indicate the presence of a needle mutilated to the point of inoperativeness. Thus, counter 25 counts the error signals from detector 23 and actuates the machine control and alarm circuits only when a predetermined number of error signals occur in consecutive operating cycles of the knitting machine. In the specific embodiment described hereinafter in connection with FIG. 3, the counter is constructed to actuate the machine control upon a count of two error signals in consecutive machine cycles. However, in an extremely noisy environment or under other operating conditions, it may be desirable to require a higher count from counter 25 before actuating control 26 or alarm 26A. A count adjustment may be provided, as indicated by a variable resistor 92.

Shutting down a knitting machine or comparable automatic production apparatus may entail considerable economic loss. Accordingly, monitor system 10 should actuate machine control 26 only if it is reasonably certain that the error signal from detector 23 actually represents a mutilated needle. One of the important protective features of monitor system 10 is range gate 24. When an error signal first appears in the output of detector 23, that error signal is supplied to the range gate. The range gate, by its connection back to detector 23, operates to prevent the generation of any additional error signals until a major portion of a machine cycle has passed subsequent to initiation of the first error signal. That is, once sensing means 16 and detector 23 have initially identified an apparent mutilated needle, detector 23 is effectively disabled for about 350 of the next machine cycle, and is then enabled so that it can detect a subsequent indication of a mutilated signal recurring at the same point on needle cylinder 12. If this were not done,

there would be no positive assurance that the system was not functioning at random in response to noise in the sensing signal supplied to detector 23.

If monitor system merely shut down the knitting machine or like apparatus in which it is used upon counting a predetermined number of error signals, substantial difficulties would still be presented. in cyclically operable machines of this kind, it is difficult to predictjust how many number of machine cycles will occur once the machine power is shut off. When the machine stops, the operator still has the almost insurmountable problem of identifying which one of the many hundreds of needles in the machine is the mutilated needle that has been detected and caused machine shutdown.

To alleviate this problem, strobe light 28 operates in conjunction with index 29 to identify the location of the mutilated needle. If the machine has already shut down, the operator can start the machine, overriding monitor system 10 and its effect upon machine control 27. When the mutilated needle is again detected, strobe light 28 flashes and illuminates one of the identification markings on index 29. The machine operator can then shut the machine down and rotate needle cylinder 12 until the same point on index 29 is aligned with marker 30; the mutilated needle is now aligned with sensing means 16. Extreme precision locating the mutilated needle is not necessary; it is sufficient if the index arrangement narrows the range to as few as 10 needles. This is particularly important with respect to bent needles, since it is almost impossible to find such needles in the hundreds constituting the array mounted on needle cylinder 12.

One major advantage of the invention is based upon the discovery that the needles in a knitting machine tend to fail in a progressive manner. Thus, the needle steel may slowly soften, due to repetitive flexure in the course of the knitting operation, creating fatigued sections in the needles. As fatigue progresses, a needle may become sufficiently softened so that it will be enough out of alignment to produce an error signal, in monitor system 10, on one machine cycle; in the next cycle the same soft needle may be back in alignment, so that counter 25 is reset and machine control 26 is not actuated. Strobe light 28, however, is actuated by every error signal and does not depend upon the operation of counter 25. Consequently, the machine operator can observe that an intermittent error signal occurs with respect to a given position on needle cylinder index 29 and can make a note of that index position. When a roll of knitted material is completed and the machine is momentarily shut down to begin a new roll, the operator may then replace one or more needles at the noted position; although those needles have been functioning, they can be expected to fail in the near future.

Monitor system 10 is also of substantial value in setup of the knitting machine or other apparatus with which it is employed. On startup, monitor system 10 is set for low sensitivity by adjusting the variable impedance 82. The sensitivity of the mom tor system is then gradually increased until an error signal is produced, actuating strobe light 28 and indicating a defective or mutilated needle at some position on the needle cylinder. inevitably, with hundreds of needles on the cylinder, a few will be out of alignment when the machine is initially set up for operation.

The first few needles detected as being mutilated, with gradually increasing sensitivity for monitor system 10, are replaced. After this has been done several times, a condition is reached in which, with the monitor system set for high sensitivity, random error signals are generated at varying points around the needle cylinder. This gives a good indication that the needles are in adequate alignment and ready for proper operation. The monitor system sensitivity can then be reduced to normal operating level, which may be determined empirically for each machine, and the operator is assured that the machine is ready to operate in an accurate and effective manner.

FIG. 3 illustrates a specific operating circuit for monitor system 10, as applied to a high-speed knitting machine. In

FIG. 3, the pickup coil 19 of sensing device 16 has one terminal connected to system ground and the other-terminal coupled through a capacitor 51 to an input terminal of an amplifier 49. A parallel RC circuit comprising a capacitor 52 and a resistor 71 is utilized to establish the gain or clipping level for amplifier 49, which is provided with a power supply connection to an appropriate DC supply designated at B+. The output of amplifier 491, which is a part of limiter amplifier 20 (FIG. 1), is connected to a coupling capacitor 53 which is in turn connected to the base electrode of a transistor 35 that is also a part of the limiter amplifier. The base of transistor 3! is also connected to a voltage divider comprising a resistor 72 that is connected to the B+ supply and a resistor 73 that is returned to system ground.

The emitter of transistor 31 is returned to ground through a resistor 75. The collector of transistor 31 is connected to the B+ supply through a load resistor 74 and is coupled to the base electrode of a transistor 32 by means of a differentiating capacitor 54. The base electrode of transistor 32 is also connected to a voltage divider comprising a resistor 76 connected to the B+ supply and a resistor 77 returned to system ground. Transistor 32 functions as an inverter amplifier for the dif' ferentiated signal derived from its input circuit comprising capacitor 54 and resistor 77.

The output for transistor 32, which is output stage of differentiator circuit 21, comprises a resistor 79 connected from the emitter of the transistor to system ground and a load resistor 78 connected from the collector to the B-lsupply. The connection to the succeeding stage, shaping amplifier 22, is taken from the collector of transistor 32 to the base electrode of a transistor 33. The collector of transistor 33 is connected directly to the B+ supply and the emitter is connected to an emitter resistor 80 that is returned to system ground. Transistor 33 is utilized as an emitter follower, the output connection being taken from the emitter of the transistor through a capacitor 55 that is connected to the gate electrode of a silicon-controlled rectifier 34 incorporated in the detector 23. The gate electrode of control rectifier 34 is also connected to a resistor 81 that is returned to system ground.

Error detector 23 is a pulse frequency anomaly detector comprising a capacitor 56 and a constant-current charging circuit 105. Circuit includes a PNP-transistor 35 having its emitter electrode connected to the B+ supply through the variable resistor 32. The collector of transistor 35 is connected to the anode of rectifier 34, the cathode of rectifier 34 being returned to system ground. Capacitor 56 is connected from the collector of transistor 35 to ground.

A diode 36 is connected from the B+ supply to the base electrode of transistor 35. Diode 36 should be matched as precisely as possible to the diode characteristics of transistor 35. To assure an effective match, diode 36 may comprise a transistor matched in type and operating characteristics to transistor 35, the collector of transistor 36 being left open-circuited. The common terminal of the base electrodes of devices 35 and 36 is returned to system ground through a resistor 83.

In addition to capacitor 56, constant-current charging circuit 105, and rectifier 34, detector 23 comprises an error signal circuit including a unijunction transistor 38. The emitter of transistor 38 is connected to the collector of transistor 35. The first base of transistor 38 is connected to the B+ supply through a resistor 84 and the second base of transistor 38 is connected to system ground through a resistor 85.

In addition to capacitor 56, constant-current charging circuit 105, and rectifier 34, detector 23 comprises an error signal circuit including a unijunction transistor 38. The emitter of transistor 38 is connected to the collector of transistor 35. The first base of transistor 38 is connected to the B+ supply through a resistor 34 and the second base of transistor 38 is connected to system ground through a resistor 85.

The output stage of the pulse frequency anomaly detector 23 comprises a signal controlled rectifier 39 having its trigger electrode coupled to the second base of transistor 38 by a differentiating circuit comprising a capacitor 59 and a resistor 93 that is returned to system ground. The anode of rectifier 39 is connected to a resistor 97 that is in turn connected to the B+ supply. The cathode of control rectifier 39 is returned to system ground through the parallel combination of a resistor 86 and a capacitor 57.

Range gate 24, in the circuit illustrated in FIG. 3, is essentially similar in construction to detector 23. But the power supply for the range gate is taken from a conductor 107 that is connected to the cathode of rectifier 39 in the output of detector 23, conductor 107 also constituting an output connection from the detector to counter 25 and to strobe light circuit 28.

Thus, range gate 24 comprises a constant-current charging circuit 106 including a transistor 40 and a matched diode 41; as before, diode 41 may comprise a transistor matched to transistor 40. The emitter of transistor 40 is connected to a variable resistor 91 that is in turn connected to conductor 107. The emitter of transistor 41 is directly connected to conductor 107. The base electrodes of transistors 40 and 41 are connected together and are returned to system ground through a resistor 90. The collector of transistor 40 is connected to a capacitor 58 that is returned to system ground. The collector of transistor 41 is open-circuited.

Range gate 24 further comprises a unijunction transistor 42 having its emitter electrode connected to capacitor 58. The first base of transistor 42 is connected to a resistor 88 that is in turn connected to conductor 107. The second base of transistor 42 is returned to ground through a resistor 89 and is also connected to the base electrode of an output transistor 43. The emitter of transistor 43 is returned to system ground and the collector is connected back to the anode of rectifier 39 in detector 23.

Counter 25, in the circuit of FIG. 3, comprises a unijunction transistor 44 having its emitter electrode connected to a capacitor 63 that is returned to ground. The emitter of transistor 44 is also connected to a variable resistor 92 that is in turn connected to the conductor 1 07 in the output circuit of detector 23. The first base of transistor 44 is connected to a resistor 93 which is in turn connected to a terminal 108 in a voltage divider comprising a resistor 100 and a resistor 101. Resistor 100 is connected to the B+ supply and resistor 101 is returned to system ground.

The second base of transistor 44 is connected to a load resistor 94 that is returned to system ground. The second base of transistor 44 is also connected to a capacitor 60 which is in turn connected to the trigger electrode of a signal controlled rectifier 45. The trigger electrode of rectifier 45 is also connected to a resistor 95 that is returned to ground.

Rectifier 45 is a part of machine control circuit 26. The cathode of the rectifier is connected to system ground. The anode of the rectifier is connected to one terminal of the operating coil 111 of a relay 112, the relay contacts being generally indicated at 113. The other terminal of coil 111 is connected, through a normally closed reset switch 114, to the B+ supply. A capacitor 61 and a diode 47 may be connected in parallel with the relay coil 111.

Strobe light 28, in the circuit illustrated in FIG. 3, comprises a conventional stroboscopic lamp 115 having one main electrode connected to system ground and the other main electrode connected to a high voltage DC supply, herein designated as C+, through a resistor 110. A capacitor 65 is connected across the main electrodes of lamp 115. The trigger electrode of lamp 115 is connected to the output winding of a strobe lamp exciting transformer 116, the input terminal of the transformer being supplied with power by the voltage divider comprising resistors 103 and 104.

The strobe light 28 further comprises a signal controlled rectifier 46 having its anode connected to the center terminal of transformer 116 and having its cathode returned to system ground. The gate electrode of rectifier 46 is connected,

through a blocking diode 48 and a capacitor 62, to the output conductor 107 of detector 23. A resistor 102 is connected from the common terminal of diode 48 and capacitor 62 to system ground. The strobe light circuit also includes a capacitor 64 connected from resistor 104 to system ground.

In considering the operation of the circuit of needle monitor 10 as illustrated in FIG. 3, it may be noted that the signal supplied to amplifier 49 through capacitor 51 is a series of pulses each indicative of the passage of one needle past the sensing means 16. If all needles are present in proper alignment, and if the needles are not broken, bent, or otherwise mutilated, this input signal to the monitor system comprises a series of pulses 121 recurring at fixed intervals as shown in FIG. 4. The sensing signal comprising pulse 121 is amplified and limited to the limiting amplifier 20 so that the signal supplied from the limiter to the differentiating circuit 21, at capacitor 54, comprises a series of pulses at equal amplitude as represented in FIG. 4 by the pulses 123. The pulse signal is then differentiated and inverted in circuit 21 and further shaped in amplifier 22, the output from the emitter-follower of amplifier 22 comprising a series of narrow pulses 125 of equal amplitude.

Each of the pulses 125 is applied to the gate electrode of the signal controlled rectifier 34, and each pulse renders rectifier 34 conductive. It should be noted that the pulses 125 must exceed a firing level of a given amplitude 127 in order to trigger rectifier 34 to conduction.

The constant current charging circuit in detector 23 supplies a current of constant amplitude to capacitor 56, building up the potential on capacitor 56 at a constant rate as indicated by the ramp voltage 129 in FIG. 4. The charge rate is adjusted, by means of variable resistor 82, so that the charge on the capacitor does not reach a given threshold level 131 within the time between consecutive pulses derived from accurately positioned unmutilated needles. Each time rectifier 34 is triggered to conduction by a pulse representative of a needle passing the sensing means of the system, capacitor 56 is rapidly discharged through rectifier 34. As long as pulse 125 triggers rectifier 34 to conduction before ramp voltage 129 can reach threshold 131, which is the conduction threshold for unijunction transistor 38, the unijunction transistor 38 remains nonconductive. This is the normal operating condition as long as no mutilated needle is detected.

Occurrence of a needle with a broken beard that does not properly bridge the gap between the pole pieces of sensing.

means 16 (FIG. 1) is generally represented by the reducedamplitude pulse 121A in FIG. 4. Pulse 121A, due to its reduced amplitude, is reflected in a reduced-amplitude pulse 123A in the output of limiter 20 and in a corresponding reduced-amplitude pulse 125A in the output of emitter follower 22 (FIG. 4). Pulse 125A is below the firing level 127 for rectifier 34; consequently, at that point in the operation of the monitor system at which rectifier 34 would normally be fired by pulse 125A, the rectifier remains nonconductive. Under these circumstances, capacitor 56 is not discharged through rectifier 34, and the ramp voltage comprising the charge on capacitor 56 builds up to the firing threshold 131 of transistor 38, as indicated by the ramp voltage segment 129A.

When the ramp voltage crosses threshold 131, as indicated by the intersection of ramp voltage 129A with threshold 131 in FIG. 4, transistor 38 becomes conductive. The resulting surge of current through resistor 85 (FIG. 3) is differentiated by the circuit comprising capacitor 59 and results in the application of a sharp pulse 133 to the gate electrode of the signal controlled rectifier 39 in the output circuit of detector 23 (see FIGS. 3 and 4). Accordingly, rectifier 39 is driven conductive and remains conductive. Resistor 97 is made very small in relation to resistor 86; consequently, when rectifier 39 becomes conductive, the voltage on conductor 107 becomes approximately equal to the total B+ voltage. The output signal from rectifier 39, which is the error signal on conductor 107, is represented in FIG. 4 by the waveform 135.

During those time intervals in which there is no error signal output from detector 23, on conductor 107, range gate 24 remains quiescent because there is no power supply for the range gate. As soon as rectifier 39 in the output of detector 23 goes conductive, however, conductor 107 is maintained at approximately the B+ voltage, as described above. Consequently, the error signal 135 affords a DC supply voltage to range gate 24 and operation of the range gate is initiated.

The basic operation of range gate 24 and counter 25 can best be understood by reference to FIG. 5, considered in conjunction with FIG. 3. When conductor 107 goes to the B+ voltage, due to the presence of the error signal on that conductor, the constant-current charging circuit 106 begins to charge capacitor 58 at a constant rate as indicated by the ramp signal 141 in FIG. 5. Capacitor 58 continues to charge until it reaches the threshold 143, which is the intrinsic standoff level for unijunction transistor 42. As soon as the charge on capacitor 58 reaches level 143, transistor 42 is triggered to conduction. The output from transistor 42 is applied to the electrode of transistor 43 and drives transistor 43 to conduction. When transistor 43 goes conductive, it effectively shunts rectifier 39 with a low-impedance path and thereby removes the anode voltage for the rectifier. Accordingly, rectifier 39 goes nonconductive, terminating error signal 135 as indicated at 145 in FIGS.

For normal operation of monitor system 10, the charge rate for capacitor 58 in ramp generator 24 is adjusted, by means of the variable resistor 91, so that the intersection of the ramp voltage 141, capacitor 58 and the firing threshold 143 for transistor 42 occurs after a major fractional portion of a machine cycle, preferably after about 350 of the machine cycle. Rectifier 39 of detector 23 remains conductive and produces a continuing error signal until the detector is reset by range gate 24, thus, the range gate effectively precludes the generation of consecutive error signals within the time interval required for ramp voltage 141 to reach threshold 143. In the complete machine cycle T1 after error signal 135 is initiated, therefore, as shown in FIG. 5, no new error signal can be generated. In this manner, the range gate limits monitor system by preventing the generation of consecutive error signals within any given machine cycle.

When an error signal appears on conductor 107 in the out put of detector 23, the counter capacitor 63 also begins to charge through variable resistor 92. In this instance, there is no necessity for a constant-current charging circuit for the capacitor because there is no real need for accurate adjustment of the timing of the charge on capacitor 63, comparable to the requirements applicable to the charging of capacitors 56 and 58. However, resistor 92 is adjusted so that, in a single machine cycle T1, the charge on capacitor 63 does not reach the conduction threshold 147 for unijunction transistor 44. The charging curve for capacitor 63 starts out as indicated by curve 149 in FIG. 5. Near the end of the first machine cycle Tl following initiation of an error signal 135, when the detector circuit 23 is reset as described above, capacitor 63 starts to discharge along the curve 151. The counter capacitor discharge path is through resistors 92 and 86. The charge on capacitor 62 is substantially completely dissipated during the next machine cycle T2, assuming that a second error signal has not been generated by detector 23 at the beginning of this machine cycle.

When an error signal is developed at conductor 107 as described above, a signal pulse is supplied to the gate electrode of the signal controlled rectifier 46 in strobe circuit 28, through the differentiating circuit comprising capacitor 62 and resistor 102. This signal triggers rectifier 46 to conduction, discharging capacitor 64 through the primary winding of transformer 116 and producing a high-amplitude pulse in the output winding of transformer 116, which is connected-to the trigger electrode of stroboscopic lamp 115. Lamp 115 fires, briefly illuminating that portion of index 29 aligned with the index marker 30 (FIG. 2) at the time the error signal is initiated. The strobe lamp is not energized again unless and until a second error signal occurs.

For the first two machine cycles T1 and T2, in FIG. 5, there is only one error signal 135, occuring in machine cycle T1. Consequently as described above, counter 25 does not reach a count sufficient to actuate machine control 26 or alarm 26A. The remaining portion of FIG. 5 illustrates the effect of two or more error signals occurring in consecutive knitting machine cycles T3-T5.

In machine cycle T3, the ramp voltage 141 on range gate capacitor 58 again reaches the intrinsic standoff voltage 143 for unijunction transistor 42. This action occurs near the end of machine cycle T3, after a time interval equal to approximately 350 of the machine cycle. During this same machine cycle T3, the charge on capacitor 63 in counter 25 builds up as indicated by curve 149. During machine cycle T3, as in the previous example, the charge on capacitor 63 does not reach the intrinsic standoff or trigger voltage 147 for unijunction transistor 44.

In the next machine cycle T4, however, an error signal 135 again occurs. Consequently, the charge on capacitor 63 cannot dissipate in accordance with curve 151A. Instead, after a short time interval following the resetting of the anomaly detector, near the end of cycle T3, the charging of capacitor 63 is resumed in cycle T4 as illustrated by curve 153. During cycle T4, the charge curve 153 for capacitor 63 intersects the threshold level for transistor 44 and transistor 44 is driven conductive. When transistor 44 goes conductive, a pulse signal is developed across its load resistor 94; this signal is differentiated by the circuit comprising capacitor 60 and resistor 95, and is applied to the gate electrode of the signal controlled rectifier 45. Rectifier 45 is thus gated to conductive condition and completes an operating circuit for coil 111 of control relay 112. In most instances, relay 112 will be connected, by contacts 113, to the energizing circuit or other control circuit of the knitting machine so that energization of the relay shuts down the machine. On the other hand, other machine control functions can be performed by actuation of the relay if desired. Once rectifier 45 has been driven conductive, it remains conductive until reset switch 114 is actuated by the machine operator to permit restarting of the knitting machine.

In the description of FIG. 4, relative to the operation of the circuit of FIG. 3, it is assumed that the error signal is generated in response to a missing or low-amplitude pulse as might be developed, in the sensing signal, through detection of a needle having a broken beard. A similar result obtains, in the sensing signal, if the needle itself is broken off or if the needle is bent away from sensing device 16. FIG. 6 affords a similar illustration of the effect of a bent needle or bent beard, where the direction of the bend is to one side of the normal needle position.

Thus, as shown in FIG. 6, one of the sensing signal pulses 1218 may be substantially displaced in time from its normal position. This result obtains in the case of a needle that is bent to one side but remains in front-to-rear alignment with the sensing device 16 to produce a pulse 1218 of sufficient amplitudes to afford a positive indication of the presence of a needle. The output signal from limiter 20 is again a series of pulses 123 or equal amplitude, but one pulse 1238 is displaced in time, occurring, substantially later than for a needle accurately positioned in the array. The corresponding signal pulse 1258 in the output of amplifier 22 is similarly delayed. Under these circumstances, the ramp voltage on capacitor 56 builds up to the threshold 131 during the time interval preceding pulse 1258 and crosses threshold 131, producing a pulse signal 133 that fires gate device 38 and triggers rectifier 39 to conduction in anomaly detector 23. Thus, as in the case of the broken needle or beard, an error signal 135 is produced on conductor 107.

The error signal produced by a bent needle is the same as that produced in the case of a broken needle. If only one error signal is developed, and there is no error signal in the next machine cycle at the same point on the array, counter 25 does not reach a count of two and machine control 26 is not actuated. Strobe light 28 is actuated, however, informing the machine operator that there is some difficulty in the functioning of the machine. On the other hand, if another error signal is developed in the next consecutive machine cycle, counter 25 reaches the count of two and actuates machine control 26 as described above.

In the circuit of H6. 3, anomaly detector 23 and range gate 24 conjointly constitute a monostable flip-flop circuit having an operating period equal to the time interval T (FIG. which is a major fractional portion of the machine operating cycle Tl. That is, whenever the timing of the sensing signal input anomaly detector 23 is such as to actuate that detector and produce an error signal output, the detector remains in an actuated state, with rectifier 39 conductive, until the detector is reset by operation of range gate 24, reset occurring when transistor 43 is driven conductive. The cooperative action of the detector and the range gate prevents excessive machine shutdown operation due to scattered noise signals that may occur in the pulse signal input to the detector, and prevents the excessive economic losses that could otherwise occur. Similarly, overcontrol on the part of the monitor system, which could result from a bent needle that functions properly much of the time but that is nearing a fatigue or failure point, is prevented by counter 25, which precludes machine shutdown unless and until two error signals are developed in consecutive machine cycles.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications without departing from the spirit thereof.

What I claim is:

1. In a monitor system for an apparatus of the kind comprising an array of individual operating elements moving at a substantially predetermined speed along a given path in accordance with a substantially predetermined repetitive operating cycle,

a. sensing means located at a first observation point on said path for generating a sensing signal comprising a series of pulses each indicative of the passage of one operating element past the observation point;

b. a pulse frequency anomaly detector coupled to said sensing means for generating error signals in response to a material displacement in timing or marked reductions in amplitude of said sensing signal pulses indicating the passage of mutilated operating elements past said observation point;

c. range gate means coupled to said detector precluding the generation of consecutive error signals within a time interval corresponding to a major fractional portion of the operating cycle of said apparatus;

d. control means coupled to said detector for controlling operation of said apparatus in accordance with said error signals and comprising: i 1. counter means coupled to said detector means for developing a control signal in response to a predetermined number of error signals, greater than unity oc' curring in consecutive operating cycles of said apparatus,

2. index means on said array, and- 3. a stroboscopic light source located at a second observation point on said path for momentarily illuminating said index in response to each error signal.

2. In apparatus for detecting the presence and location of a defective one of a plurality of normally identical elements which cyclically move past a common position,

a. means effective to generate a signal in response to the passage by said common position of a defective element, and

b. means utilizing said signal positively to indicate which of said elements is the defective one and comprising:

1. a strobe light which is energized in response to the signal produced by means (a), and

2. markings associated with the location occupied by the defective element which are observable when illuminated by the strobe light, thereby visually to locate said defective element. 

1. In a monitor system for an apparatus of the kind comprising an array of individual operating elements moving at a substantially predetermined speed along a given path in accordance with a substantially predetermined repetitive operating cycle, a. sensing means located at a first observation point on said path for generating a sensing signal comprising a series of pulses each indicative of the passage of one operating element past the observation point; b. a pulse frequency anomaly detector coupled to said sensing means for generating error signals in response to a material displacement in timing or marked reductions in amplitude of said sensing signal pulses indicating the passage of mutilated operating elements past said observation point; c. range gate means coupled to said detector precluding the generation of consecutive error signals within a time interval corresponding to a major fractional portion of the operating cycle of said apparatus; d. control means coupled to said detector for controlling operation of said apparatus in accordance with said error signals and comprising:
 1. counter means coupled to said detector means for developing a control signal in response to a predetermined number of error signals, greater than unity occurring in consecutive operating cycles of said apparatus,
 2. index means on said array, and
 3. a stroboscopic light source located at a second observation point on said path for momentarily illuminating said index in response to each error signal.
 2. index means on said array, and
 2. markings associated with the location occupied by the defective element which are observable when illuminated by the strobe light, thereby visually to locate said defective element.
 2. In apparatus for detecting the presence and location of a defective one of a plurality of normally identical elements which cyclically move past a common position, a. means effective to generate a signal in response to the passage by said common position of a defective element, and b. means utilizing said signal positively to indicate which of said elements is the defective one and comprising:
 3. a stroboscopic light source located at a second observation point on said path for momentarily illuminating said index in response to each error signal. 